8 Learning Objectives (1 of 15)• Compare an offensive fire attack to a defensive fire attack, explaining the basics of each type of attack and identifying the rationale for each strategy.• Describe trial-and-error methods of calculating rate of flow.
8 Learning Objectives (2 of 15)• Explain the theory of indirect extinguishment.• Compare conditions within a fire compartment after pulsing versus after an indirect attack.
8 Learning Objectives (3 of 15)• Analyze rate-of-flow requirements using V/100, A/3, and sprinkler calculations.• Define a ventilation-controlled fire.• Define a fuel-controlled fire.
8 Learning Objectives (4 of 15)• Describe “area of involvement” and how it applies to rate-of-flow calculations.• Write a brief position paper outlining the advantages of using the Royer/Nelson (V/100) rate-of-flow formula.
8 Learning Objectives (5 of 16)• Explain why a fire attack meeting or exceeding the calculated rate of flow could fail to extinguish the fire.• Explain the relationship between nozzle type, rate of flow, and nozzle reaction force.
8 Learning Objectives (6 of 15)• Discuss the advantages and disadvantages of using an aerial device as a portable standpipe.• Describe extinguishment of ordinary combustibles by inhibiting pyrolysis.
8 Learning Objectives (7 of 15)• Discuss the dangers of opposing fire streams and ways to avoid opposing fire streams.• Define external exposure.• Define internal exposures.• List factors to consider when evaluating external exposures.
8 Learning Objectives (8 of 15)• Describe the purpose of a backup line and how it can be used to protect fire fighters attacking the fire.• Evaluate water supply requirements based on rate of flow and other factors.
8 Learning Objectives (9 of 15)• Examine the relationship and proper use of ventilation during offensive extinguishment operations.• Describe the factors that determine the number of apparatus needed at an offensive operation.
8 Learning Objectives (10 of 15)• Discuss apparatus management at a medium- to large-scale incident.• Develop a list of advantages and disadvantages when using Class A foam during structural firefighting.
8 Learning Objectives (11 of 15)• Compute and compare the rate of flow for various areas using A/3 and V/100.• Evaluate the available flow from standard pre-connected hose lines and determine when the rate of flow for a structure should be pre-incident planned.
8 Learning Objectives (12 of 15)• Estimate the number and size of hose lines needed to apply a calculated rate of flow.• Assess staffing requirements for an offensive attack based on rate-of-flow and life safety factors.
8 Learning Objectives (13 of 15)• Assess the probability of an imminent life-threatening situation.• Compare staffing available to staffing requirements.
8 Learning Objectives (14 of 15)• Using a fire scenario, assess the total water supply available and apparatus needs in terms of required fire flow.• Given fire conditions and location, determine the ventilation possibilities and choose the best ventilation method(s).
8 Learning Objectives (15 of 15)• Evaluate the flow available from a standpipe system and standard fire department standpipe equipment based on a calculated rate of flow.• Examine and evaluate various attack positions in a multi-story building.• Discuss factors involved in choosing an offensive strategy.
8 Overview• Offensive versus defensive fire attack – Based on staffing levels and risk–benefit analysis• Rate-of-flow – Determines number and size of hose lines• Resource capabilities must meet incident requirements
8 Calculating Rate of Flow• Methods – Clark’s calculation – Trial and error – Royer/Nelson formula – National Fire Academy formula – Sprinkler calculations• Cannot predict every variable
8 Indirect Application• Lloyd Layman – Coast Guard tests – Based on water converting to steam – Reduced water use = less property damage – Disrupts heat balance • Decreases chances for occupant survival • Increases chances for fire fighter steam burns
8 Royer/Nelson Formula (1 of 2)• V/100 = Volume in cubic feet divided by 100• Oxygen controlled fires – Require less water• Valid for most fires – Accounts for ceiling heights• Recommended for pre-planning
8 Sprinkler Calculations (1 of 2)• Most accurate• Considers fuel load and type• Useful in pre-planning• Published in NFPA documents and Factory Mutual Data Sheets• NFPA 13: Standard for the Installation of Sprinkler Systems
8 Sprinkler Calculations (2 of 2)• Variables: – Building type – Number of floors – Occupancy type – Commodity inside the structure – Storage configuration of the commodity
8 Stages of Fire• Early stages: fuel dependant• Late stages: oxygen dependant• Well involved fires controlled by both• Once ventilated, fire reacts to type and amount of fuel.
8Estimating Compartment Size• Rate-of-flow based on area or volume of compartment(s) on fire• Calculating each area separately is recommended. – Provide flow needed for largest area.• Fire fighters can estimate size for IC.
8 Pre-Planning by Occupancy• One- and two-family dwellings• Apartment buildings – Common areas• Small businesses
8Estimating Percent of Area on Fire• Royer/Nelson – Volume of enclosure – Doesn’t consider modifying formula• NFA – Area of involvement – Percentage-of-involvement modifier recommended
8 Comparing Rate-of-Flow Calculations (1 of 2)• Sprinkler calculations, variables: – Building type – Number of floors – Occupancy type – Commodity – Storage configuration• Most accurate• Based on actual fire experience
8 Comparing Rate-of-Flow Calculations (2 of 2)• U.S. National Fire Academy system – Yields higher rate of flow – Field-estimated – Overestimation leads to quicker extinguishment with less water – Gross overestimation may cause a delay in attack
8 Which Rate-of-Flow Calculation Is Best?• Each method has merit.• If fuel load is heavy, sprinkler calculations should be used.• A/3 formula may be easier, but may not be as accurate.• Each formula must be modified based on trial and error.
8 Selecting Attack Hose Size• Booster hose inappropriate for structure fires• 1¾” (44-mm) attack hose lines recommended as a minimum – With backup hose line, will be adequate to extinguish most fires• Mobility decreases, flow increases with 2½” (64-mm)
8 Nozzle Flow Rates• Flow rates vary according to: – Nozzle pressure – Pump discharge pressure – Length of hose lay
8 Nozzle Flow Ratings• Variable-stream nozzles rated by: – Pump discharge pressure and the length of hose, or – Nozzle pressure• Smooth-bore nozzles rated by: – Nozzle pressure
8 Nozzle Reaction Force• Increases as the flow and nozzle pressure increase• Makes nozzle more difficult to control• If reaction force is too great: – Flow should be reduced – Nozzle should be replaced with one that is easier to control
8 Portable Standpipes• Aerial ladder – Limited to height of ladder• Pre-piped waterway• Pressures supplied by apparatus pumps – Eliminates potential standpipe problems• Can be used in buildings not standpipe equipped
8 Nozzle Selection• Variable-stream versus smooth bore• Stream force – Affects the distance the stream will carry – Allows the crew to access hidden fires• Fog streams – Stop forward extension of fire – Provide exposure protection
8Selecting Stream Position (1 of 3)• Indirect attack – Little application to structural firefighting – Steam production is dangerous • Poor choice in occupied areas – Useful in unoccupied basements, attics, or storage areas – Piercing nozzles
8Selecting Stream Position (2 of 3)• Direct attack – Preferred – Applies water directly on the burning material • Reduces temperature of the fuel • Reduces or eliminates combustible vapors
8Selecting Stream Position (3 of 3)• Combination attack – Direct and indirect application – Dangerous for interior application • Disturbs heat balance • Generates intense steam
8 Hose Line Placement• Risk-versus-benefit analysis• First line should be placed between the victim and the fire. – Coordinated with entry and ventilation• Objective is to get water directly on the fuel.
8 Number of Attack Lines• Based on flow requirements• A single 1¾” (44-mm) hose line for most dwelling fires• Backup hose line – Protects egress routes – Bolsters attack
8 Evaluating Exposures• Internal – Natural pathways • Concealed spaces, stairs, chutes, and shafts • Vertically up the exterior of the building from windows or other openings
8 External Exposures (1 of 2)• Adjacent buildings• Improper ventilation can expose buildings.• Consider fire apparatus and equipment parked near the fire building.
8 Factors to Consider• Proximity to the fire building• Wind direction• Height of exposure• Life hazard in the exposure• Hazard presented by the exposed occupancy
8 Backup Lines• Protect the crew on the initial attack line – Also provide additional flow if needed• At least as large as the initial attack line
8 Additional Lines• To meet the rate of flow in the immediate fire area• Backup hose line(s) for immediate fire area• To protect egress routes• To protect internal/external exposures• Other backup hose lines as needed
8 Water Supply Needs• Large diameter hose effective• Two supplies recommended• Shouldn’t rely solely on water tank supply• Must supply calculated rate-of-flow – Plus backup/exposure lines
8 Ventilation Needs• Used to assist in extinguishment efforts – Allows approach to fire – Controls fire spread – Makes conditions tenable• Venting to support extinguishment – Timing is crucial – Charged lines must be in place• Improper venting can extend fire
8 Staffing Needs• Based on: – Rate of flow – Backup lines – Placement of lines above the fire – Secondary water supply
8 Initial Response• NFPA 1710 – Defines tasks and minimum staffing for the initial response – If needs not met, must call for mutual aid or additional alarms
8 Apparatus Needs• Normally sufficient for initial response to offensive operation• Proper positioning crucial• Use only those necessary to meet tactical objectives.• Large scale incident or staging area – Staging officer – Staged apparatus: staffed – Out of service apparatus: not staffed
8 Class A Foam (1 of 2)• Wildland and wildland/urban interface uses: – Pre-wetting fuels – Providing a foam layer on an exposure • Reduces radiant heat absorption – Suppression agent – Wetting agent • Resulting in greater penetration
8 Class A Foam (2 of 2)• Useful in areas with a marginal water supply• Less water damage because less water is used
8 Summary• Considerations for a safe and effective offensive operation – Sufficient personnel and resources: • to deliver the required rate of flow • to protect the fire fighters• Rate-of-flow formulas – Most valuable when included in pre-plans – V/100 or sprinkler charts used in pre-plans
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